Power Supply and Method of Supplying Power To Load

ABSTRACT

A power supply includes an inverter configured to convert direct current (DC) power into alternating current (AC) power, an impedance matching circuit configured to supply the AC power to a load, and a controller configured to detect a delay time of an output voltage and an output current output to the impedance matching circuit and the load and to adjust a frequency of the output voltage according to the detected delay time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority toPCT/KR2018/006607 filed on Jun. 11, 2018, which claims priority to KoreaPatent Application No. 10-2017-0079848 filed on Jun. 23, 2017, theentireties of which are both hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to electronic or electrical devices and,more particularly, to a power supply and a method of supplying power toa load.

BACKGROUND

Various electronic or electrical devices for use in living or industrialsites require a power supply. According to purposes, characteristics oruse environment of electronic or electrical device, the electronic orelectrical devices may require different types of power supply. Amongthe electronic or electrical devices, particularly, inductively coupledplasma (ICP) devices require an alternating current (AC) power supplyhaving high power and a high frequency.

A power supply configured to supply power to an inductively coupledplasma device may turn on or off an inverter to controls power suppliedto the inductively coupled plasma device. A power supply method of thepower supply needs to be controlled to prevent noise or stress generatedfrom the power supply and to efficiently supply power to the inductivelycoupled plasma device.

Additionally, a power amount of power supplied to the inductivelycoupled plasma device or a current amount of a current supplied theretoshould be controlled to precisely control an operation of theinductively coupled plasma device. Various methods have been studied tocontrol a power amount of power supplied to the inductively coupledplasma device or a current amount of a current supplied thereto.However, most of the methods increase the complexity, volume or price ofa power supply. Alternatively, high-frequency switching noise isgenerated in a power supply or a stress is applied to the power supplyto cause malfunction of the power supply. Thus, reliability of the powersupply is degraded or life of the power supply is significantly reduced.Accordingly, there is a need for a research into a power supply and amethod of supplying power which do not increase complexity and do notcause high-frequency switching noise and a stress.

SUMMARY

Example embodiments of the present disclosure provide a power supply anda method of supplying power which have improved reliability withoutincreasing complexity and causing high-frequency switching noise andstress.

Example embodiments of the present disclosure provide a power supply anda method of supplying power which automatically compensate for a phasedifference between an output voltage and an output current.

A power supply according to an example embodiment of the presentdisclosure includes an inverter configured to convert direct current(DC) power into alternating current (AC) power, an impedance matchingcircuit configured to supply the AC power to a load, and a controllerconfigured to detect a delay time of an output voltage and an outputcurrent output to the impedance matching circuit and the load and toadjust a frequency of the output voltage according to the detected delaytime.

In example embodiments, the controller may increase the frequency of theoutput voltage when the detected delay time is less than a first time.

In example embodiments, the controller may decrease the frequency of theoutput voltage when the detected delay time is greater than a secondtime.

In example embodiments, the controller may maintain the frequency of theoutput voltage when the detected delay time is less than or equal to thesecond time and greater than or equal to the first time.

In example embodiments, the controller may calculate an average of delaytimes detected from the output voltage and the output current and mayincrease the frequency of the output voltage when the average is lessthan the first time.

In example embodiments, the controller may store k detected delay times(k being a positive integer) and may calculate an average of the kdetected delay times.

In example embodiments, the controller may store the subsequent kdetected delay times and may calculate the average of the k detecteddelay times after calculating the average and adjusting the frequency ofthe output voltage depending on the calculated average.

In example embodiments, the controller may adjust the k.

In example embodiments, the controller may increase the frequency of theoutput voltage when, among delay times detected from the output voltageand the output current, delay times less than a first time are dominant.

In example embodiments, the controller may determine that the delaytimes less than the first time are dominant, when the number of thedelay times less than the first time is greater than or equal toone-third of the number of the detected delay times.

In example embodiments, the controller may store k detected delay times(k being a positive integer) and may determine dominant delay timesamong the stored k detected times.

In example embodiments, the controller may immediately increase thefrequency of the output voltage without determination of the dominantdelay times when n continuous delay times (n being a positive integerless than k) are less than the first time.

In example embodiments, the power supply may further include atransformer inductively coupled to a wiring between the inverter and theload and configured to output a first signal having a current of thesame phase as an output current provided to the load and a comparatorconfigured to output a second signal indicating the phase of the outputcurrent from an output signal of the transformer and to output thesecond signal to the controller.

In example embodiments, the inverter may include a first transistor anda first diode coupled in parallel between a power supply node and afirst output node, a second transistor and a second diode coupled inparallel between the first output node and a ground node, a thirdtransistor and a third diode coupled in parallel between the ground nodeand a second output node, and a fourth transistor and a fourth diodecoupled in parallel between the power supply node and the second outputnode. The first output node and the second output node may be connectedto the impedance matching circuit, and the controller may controlrespective voltages of gates of the first to fourth transistors.

In example embodiments, the controller may adjust the frequency of theoutput voltage depending on a phase difference between the second signaland a switching signal provided to the first transistor.

In example embodiments, the inverter may further include an inductorcoupled between the first output node and the second output node.

In example embodiments, the controller may be further configured toadjust dispositions of a powering period, in which the inverter outputsthe AC power, and a freewheeling period, in which the inverter does notoutput the AC power, such that the inverter adjusts an amount of powerper unit time supplied to the load through the impedance matchingcircuit.

In example embodiments, the controller may adjust the frequency of theoutput voltage according to the same characteristics when the delaytimes continuously exhibit the same characteristics.

A method of supplying power to a load includes detecting a delay time ofan output voltage and an output current output to the load and adjustinga frequency of the output voltage depending on the detected delay time.

In example embodiments, the detecting and the adjusting may be repeateduntil the delay time falls within a predetermined range.

In example embodiments, the delay time may include an average of delaytimes.

In example embodiments, the adjusting may include storing delay times,counting the number of delay times less than a first time, among thestored delay times, as a first count, counting the number of delay timesgreater than a second time, among the stored delay times, as a secondcount, counting the number of delay times greater than or equal to thefirst time and less than or equal to the second time as a third count,and adjusting the frequency of the output voltage depending a dominantcount among the first to third counts.

In example embodiment, the adjusting may include adjusting the frequencyof the output voltage according to the same characteristics when delaytimes continuously exhibit the same characteristics.

In example embodiments, the method may further include receiving atarget power amount, comparing an amount of power supplied to the loadwith the target power amount, adjusting a powering period, in whichalternating current (AC) power is supplied to the load, and afreewheeling period, in which the AC power is not supplied to the load,such that the target power amount and the amount of power per unit timebecome equal to each other, depending on a comparing result, andsupplying power to the load according to the adjusted powering andfreewheeling periods.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more apparent in view of the attacheddrawings and accompanying detailed description. The embodiments depictedtherein are provided by way of example, not by way of limitation,wherein like reference numerals refer to the same or similar elements.The drawings are not necessarily to scale, emphasis instead being placedupon illustrating aspects of the present disclosure.

FIG. 1 is a block diagram of a power supply system according to anexample embodiment of the present disclosure.

FIG. 2 is a detailed circuit diagram of an inverter, an impedancematching circuit, and a load according to an example embodiment of thepresent disclosure.

FIG. 3 illustrates an example in which a controller controls first tofourth switching signals.

FIG. 4 illustrates an example in which dead time is added to first tofourth switching signals.

FIG. 5 illustrates an example of waveforms of an output voltage and anoutput current depending on lapse of time when a frequency of the outputvoltage and a resonant frequency of a load match each other.

FIG. 6 illustrates an example of waveforms of an output voltage and anoutput current depending on lapse of time when a frequency of the outputvoltage is lower than a resonant frequency of a load.

FIG. 7 illustrates an operating state of an inverter when an outputvoltage transitions from a high level to a low level according to thewaveform of FIG. 6.

FIG. 8 illustrates an example of waveforms of an output voltage and anoutput current depending on lapse of time when a frequency of the outputvoltage is higher than a resonant frequency of a load match each other.

FIG. 9 illustrates an operating state of an inverter when an outputvoltage transitions from a high level to a low level according to thewaveform of FIG. 8.

FIG. 10 is a block diagram of a power supply system according to anapplication example of the present disclosure.

FIG. 11 is a block diagram illustrating an example of a controller inFIG. 10.

FIG. 12 illustrates an example in which a filtered current and phaseinformation are detected from an output current.

FIG. 13 illustrates an example of phases of a first switching signal andan output voltage.

FIG. 14 illustrates an example of a method of controlling a frequency ofan output voltage by a power supply.

FIG. 15 illustrates another example of a method of controlling afrequency of an output voltage by a power supply.

FIG. 16 illustrates another example of a method of controlling afrequency of an output voltage by a power supply.

FIG. 17 illustrates another example of a method of adjusting a frequencyof an output voltage by a power supply.

FIG. 18 illustrates an inverter, an impedance matching circuit, and aload according to an application example of the present disclosure.

FIG. 19 illustrates variations in an output current and an inductorcurrent with the lapse of time.

FIG. 20 illustrates an example of a method of controlling powerdepending on DC voltage conversion.

FIG. 21 illustrates an example of a method of controlling powerdepending on phase shift.

FIG. 22 illustrates an example in which first to fourth switchingsignals and an output voltage are adjusted according to pulse widthmodulation.

FIG. 23 illustrates an example of a method of controlling poweraccording to pulse width modulation.

FIG. 24 illustrates a method of supplying power according to an exampleembodiment of the present disclosure.

FIG. 25 illustrates an example of a variation in an inductor currentwhen an output voltage has a freewheeling period.

FIG. 26 illustrates another example of a variation in an inductorcurrent when an output voltage has a freewheeling period.

FIG. 27 illustrates another example of a variation in an inductorcurrent when an output voltage has a freewheeling period.

FIG. 28 is a block diagram of a power supply system including ahalf-bridge circuit according to another example embodiment of thepresent disclosure.

DETAILED DESCRIPTION

Example embodiments of the present disclosure will now be describedbelow more fully with reference to accompanying drawings. The presentdisclosure may, however, be embodied in different forms and should notbe constructed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the present inventionto those skilled in the art.

Reference numerals are indicated in detail in example embodiments of thepresent disclosure, and their examples are represented in referencedrawings. In every possible case, like reference numerals are used forreferring to the same or similar elements in the description anddrawings.

FIG. 1 is a block diagram of a power supply system 100 according to anexample embodiment of the present disclosure. Referring to FIG. 1, thepower supply system 100 includes AC power 110, a power supply 120, and aload 140. The AC power 110 may be a 60 Hz power used in a house or anindustrial field. The load 140 may be an electrical or electronic deviceused in a house or an industrial field. For example, the load 140 may bean inductively coupled plasma (ICP) device.

The power supply 120 may convert first AC power into second AC power andmay supply the second AC power to the load 140. For example, the secondAC power may have a frequency of several hundreds of kilohertz (kHz) totens of megahertz (MHz) and may have power of several kilowatts (kW) ormore. The power supply 120 may include a rectifier 121, a capacitor 122,an inverter 123, an impedance matching circuit 130, and a controller125.

The rectifier 121 may convert an output of the AC power 110 into DCpower. For example, the rectifier 121 may supply DC power between aground node GND and a power supply node VP. The capacitor 122 may beconnected between the power supply node VP and the ground node GND. Thecapacitor 122 may discharge an AC component transmitted to the powersupply node VP to the ground node GND.

The inverter 123 may receive the DC power from the power supply node VPand the ground node GND. The inverter 123 may receive switching signalsSW from the controller 125. The inverter 123 may convert the DC powerinto second AC power in response to the switching signals SW. The secondAC power may be supplied to the load 140 through the impedance matchingcircuit 130. The impedance matching circuit 130 may provide matching foran impedance of the load 140.

The controller 125 may transmit the switching signals SW to the inverter123. The controller 125 may control the switching signals SW such thatthe inverter 123 converts the DC power to the second AC power. Thecontroller 125 may also control the switching signals SW to regulate theamount of power supplied from the inverter 123 to the load 140. Forexample, the controller 125 may control the switching signals SW suchthat the inverter 123 supplies power through powering and freewheelingperiods according to an example embodiment. The powering and thefreewheeling periods will be described below in more detail.

FIG. 2 is a detailed circuit diagram of an inverter 123, an impedancematching circuit 130, and a load 140 according to an example embodimentof the present disclosure. Referring to FIGS. 1 and 2, the inverter 123may include first to fourth transistors TR1 to TR4 and first to fourthdiodes D1 to D4.

The first and second transistors TR1 and TR2 may be coupled in seriesbetween a power supply node VP and a ground node GND. The first diode D1may be connected in parallel to the first transistor TR1, and the seconddiode D2 may be connected in parallel to the second transistor TR2. Thethird and fourth transistors TR3 and TR4 may be coupled in seriesbetween the ground node GND and the power supply node VP. The thirddiode D3 may be connected in parallel to the third transistor TR3, andthe fourth diode D4 may be connected in parallel to the fourthtransistor TR4. As an example, the first to fourth diodes D1 to D4 maybe body diodes or Schottky diodes.

First to fourth switching signals SW1 to SW4 may be transmitted to gatesof the first to fourth transistors TR1 to TR4, respectively. That is,the first to fourth transistors TR1 to TR4 may operate in response tothe first to fourth switching signals SW1 to SW4, respectively. Thefirst to fourth switching signals SW1 to SW4 may correspond to theswitching signals SW shown in FIG. 1.

A node between the first and second transistors TR1 and TR2 and a nodebetween the third and fourth transistors TR3 and TR4 may be outputnodes. The output nodes may transmit an output voltage VO to theimpedance matching circuit 130 and the load 140. The output nodes maytransmit an output current IO to the impedance matching circuit 130 andthe load 140.

As an example, the impedance matching circuit 130 may include acapacitor C. However, an internal configuration of the impedancematching circuit 130 is not limited to a single capacitor. As anexample, the load 140 may be an inductively coupled plasma (ICP) device.The load 140 may be modeled as an inductor Lpla and a resistor Rpla. Thecapacitor C, the inductor Lpla, and the resistor Rpla may be coupled inseries between the output nodes of the inverter 123.

FIG. 3 illustrates an example in which a controller 125 controls firstto fourth switching signals SW1 to SW4.

In FIG. 3, horizontal axes indicate time T and vertical axes indicatefirst to fourth switching signals SW 1 to SW 4 and an output voltage. Aunit of the vertical axes may be a voltage V. Referring to FIGS. 1 to 3,the first and third switching signals SW1 and SW3 are controlled in asingle pair, and the second and fourth switching signals SW2 and SW4 maybe controlled in a single pair

When the first switching signal SW1 has a high level, the thirdswitching signal SW3 may also have a high level. When the firstswitching signal SW1 has a low level, the third switching signal SW3 mayalso have a low level. Similarly, when the second switching signal SW2has a high level, the fourth switching signal SW4 may also have a highlevel. When the second switching signal SW2 has a low level, the fourthswitching signal SW4 may also have a low level.

The first and third switching signals SW1 and SW3 and the second andfourth switching signals SW2 and SW4 may be complementarily controlled.For example, when the first and third switching signals SW1 and SW3 havea high level, the second and fourth switching signals SW2 and SW4 mayhave a low level. When the first and third switching signals SW1 and SW3have a low level, the second and fourth switching signals SW2 and SW4may have a high level.

When a specific switching signal has a high level, a transistor to whichthe specific switching signal is transmitted may be turned on. When aspecific switching signal has a low level, a transistor to which thespecific switching signal is transmitted may be turned off.

When the first and third transistors TR1 and TR3 are turned on and thesecond and fourth transistors TR2 and TR4 are turned off, the firsttransistor TR1 may transmit a voltage at a power supply node VP and thethird transistor TR3 may transmit a voltage at a ground node GND. Thus,the output voltage VO may have a positive value while the output currentIO may have a positive value. That is, the output current IO may flow ina direction shown in FIG. 2.

When the first and third transistors TR1 and TR3 are turned off and thesecond and fourth transistors TR2 and TR4 are turned on, the secondtransistor TR2 may transmit a voltage at the ground node GND and thefourth transistor TR4 may transmit a voltage at the power supply nodeVP. Thus, the output voltage VO may have a negative value while theoutput current IO may have a negative value. That is, the output currentmay flow in a reverse direction of the direction shown in FIG. 2.

FIG. 4 illustrates an example in which dead time DT is added to first tofourth switching signals SW1 to SW4. In FIG. 4, horizontal axes indicatetime T and vertical axes indicate first to fourth switching signals SW1to SW4 and an output voltage VO. A unit of the vertical axes may be avoltage V.

As compared to FIG. 3, there is a dead time DT between a time point atwhich the first and third switching signals SW1 and SW3 transition froma high level to a low level and a time point at which the second andfourth switching signals SW2 and SW4 transition from a low level to ahigh level. Similarly, there is a dead time DT between a time point atwhich the first and third switching signals SW1 and SW3 transition froma low level to a high level and a time point at which the second andfourth switching signals SW2 and SW4 transition from a high level to alow level.

For the dead time DT, the first to fourth switching signals SW1 to SW4all have low levels. That is, the first to fourth transistors TR1 to TR4are turned off. The dead time DT may prevent the power supply node VPand the ground node GND from being short-circuited. For the dead timeDT, the output voltage VO may have a level determined depending on avoltage and a current before the dead time DT and the operation timingof the first to fourth transistors TR1 to TR4.

Hereinafter, to avoid the complexity of description, first to fourthswitching signals SW1 to SW4 and an output voltage VO will be shownwhile omitting dead time DT unless the dead time DT is necessary forexplanation of the present inventive concepts. Even when the dead timeDT is not explicitly shown or mentioned, it is not interpreted that thedead time DT is not intended to exist.

FIG. 5 illustrates an example of waveforms of an output voltage VO andan output current IO depending on lapse of time T when a frequency fswof the output voltage VO and a resonant frequency f0 of a load 140 matcheach other. Referring to FIGS. 1, 2, and 5, phases of the output voltageVO and the output current IO may match each other when the frequency fswof the output voltage VO and the resonant frequency f0 of the load 140match each other.

As an example, the resonant frequency f 0 of the load 140 may bedetermined by an inductor Lpla of the load 140 and a capacitor C of theimpedance matching circuit 130. The resonant frequency f0 of the load140 may be determined by Equation (1).

$\begin{matrix}{{f0} = \frac{1}{2\pi \sqrt{{Lpla} \cdot C}}} & {{Equation}\mspace{14mu} (1)}\end{matrix}$

FIG. 6 illustrates an example of waveforms of an output voltage VO andan output current IO depending on lapse of time T when a frequency fswof the output voltage VO is lower than a resonant frequency f0 of a load140. Referring to FIGS. 1, 2, and 6, a phase of the output voltage VOmay lag behind a phase of the output current IO when the frequency fswof the output voltage VO is lower than the resonant frequency f0 of aload 140.

FIG. 7 illustrates an operating state of an inverter 123 when an outputvoltage VO transitions from a high level to a low level according to thewaveform of FIG. 6. Referring to FIGS. 4, 6, and 7, there may be deadtime DT when the output voltage VO transitions from a high level to alow level. For the dead time DT, the first to fourth transistors TR1 toTR4 may be turned off.

The output current IO flows to the inverter 123 from the load 140 andthe impedance matching circuit 130. Due to a direction of the outputcurrent IO, the second and fourth diodes D2 and D4 do not pass thecurrent, and the first and third diodes D1 and D3 pass the current. Thatis, when the phase of the output voltage VO lags behind the phase of theoutput current IO, the output current IO flows to the inverter 130 fromthe load 140 and the impedance matching circuit 130 for the dead timeDT.

As the output current IO flows, power may unnecessarily consumed.Moreover, as the output current IO flows, the output voltage VO of theinverter 123 is maintained at a voltage difference between the powersupply node VP and the ground node GND. The output voltage VO is appliedto opposite ends of each of the second and fourth transistors TR2 andTR4.

When the dead time DT finishes, the second and fourth transistors TR2and TR4 are turned on while a high voltage (for example, the outputvoltage VO) is applied to opposite ends of each of the second and fourthtransistors TR2 and TR4, which may be an unnecessary stress applied tothe second and fourth transistors TR2 and TR4 and may degrade the secondand fourth transistors TR2 and TR4.

Since the first to fourth transistors TR1 to TR4 of the inverter 123 aresymmetrically disposed, the same phenomenon may occur in the first andthird transistors TR1 and TR3. For example, for the dead time DT whenthe output voltage VO transitions from a low level to a high level,power may be unnecessarily consumed and a stress may generated in thefirst and third transistors TR1 and TR3.

FIG. 8 illustrates an example of waveforms of an output voltage VO andan output current IO depending on lapse of time T when a frequency fswof the output voltage VO is higher than a resonant frequency f0 of aload 140 match each other. Referring to FIGS. 1, 2, and 8, a phase ofthe output voltage VO may lead a phase of the output current IO when thefrequency fsw of the output voltage VO is higher than the resonantfrequency f0 of the load 140.

FIG. 9 illustrates an operating state of the inverter 123 when an outputvoltage VO transitions from a high level to a low level according to thewaveform of FIG. 8. Referring to FIGS. 4, 8 and 9, there may be deadtime DT when the output voltage VO transitions from a high level to alow level. For the dead time DT, the first to fourth transistors TR1 toTR4 may be turned off.

Since the output current IO has a positive value, the output current IOflows from the inverter 123 to the impedance matching circuit 130 andthe load 140. A direction of the output current IO may prevent theoutput current IO from flowing through the first to fourth diodes D1 toD4. Instead, the output current IO may flow through parasitic capacitors(not shown) of the first and third transistors TR1 and TR3.

As the output current IO flows, opposite end voltages of each of thefirst and third transistors TR1 and TR3 may increase by a voltagedifference between the power supply node VP and the ground node GND.Resonance (for example, parasitic resonance) may occur due to theparasitic capacitors (not shown) of the first and third transistors TR1and TR3 and parasitic inductors (not shown) of wirings when the outputcurrent IO flows. The parasitic resonance increases as the intensity ofthe output current IO increases, and may high-frequency switching noise.

While the output current flows through the first and third transistorsTR1 and TR3, the first and third transistors TR1 and TR3 are turned offat the dead time DT, which may act as a stress on the first and thirdtransistors TR1 and TR3. Since the first to fourth transistors TR1 toTR4 are symmetrically disposed, the same high-frequency switching noiseand stress may be generated in the second and fourth transistors TR2 andTR4 when the output voltage VO transitions from the low level to thehigh level.

As described above, when the frequency fsw of the output voltage VO isdifferent from the resonant frequency f0 of the load 140, a stress maybe applied to the first to fourth transistors TR1 to TR4 or power may beunnecessarily consumed. Thus, the frequency fsw of the output voltage VOshould be controlled similarly to the resonant frequency f0 of the load140 to improve reliability and performance of the power supply 120.

In detail, the frequency fsw of the output voltage VO is slightly higher(for example, about 0.1 to 10 percent) than the resonance frequency f0of the load 140. When the frequency fsw of the output voltage VO isslightly higher than the resonance frequency f0 of the load 140, theinstantaneous intensity of the output current IO have a fine positivevalue (for example, 0.1 percent to 10 percent of a maximum) in the stateof the dead time DT of FIG. 8.

In the situation described with reference to FIGS. 8 and 9, the firstand third transistors TR1 and TR3 are turned off while a minute currentflows. Therefore, the stress applied to the first and third transistorsTR1 and TR3 is negligible. For the dead time DT, as the output currentIO flows, the opposite end voltages of each of the first and thirdtransistors TR1 and TR3 increase by a voltage difference between thepower supply node VP and the ground node GND.

For the dead time DT, opposite end voltages of each of the second andfourth transistors TR2 and TR4 decrease to 0 volt (or a similar lowvolt) as the output current IO flows. That is, when the dead time DTfinishes and the second and fourth transistors TR2 and TR4 are turnedon, the opposite end voltages of each of the second and fourthtransistors TR2 and TR4 are 0 volt. Therefore, the second and fourthtransistors TR2 and TR4 are negligible.

Likewise, when the phase of the output voltage VO is controlled tominutely lead the phase of the output current IO (for example, 0.1% to10%), transistors may perform a preferable switching operation calledzero voltage nearly zero current switching (ZVZCS). According to theZVZCS, the first to fourth transistors TR1 to TR4 of the inverter 123may be stably controlled. The controller 125 may control the first tofourth switching signals SW1 to SW4 according to the ZVZCS.

To perform the ZVZCD, an operating frequency of the power supply 120should match a resonant frequency of the load 140. The resonantfrequency of the load 140 is determined depending on physicalcharacteristics of the load 140. Accordingly, to match the operatingfrequency with the resonant frequency, the power supply 120 needs tounderstand the operating frequency and perform a function to match theoperating frequency to the resonant frequency.

FIG. 10 is a block diagram of a power supply system according to anapplication example of the present disclosure. Referring to FIG. 10, apower supply system 200 includes AC power 210, a power supply 220, and aload 240. The power supply 220 includes a rectifier 221, a capacitor222, an inverter 223, a controller 225, a transformer 226, a filter 227,and a comparator 228.

The rectifier 221, the capacitor 222, the inverter 223, and theimpedance matching circuit 230 have the same structures as describedwith reference to FIG. 1 and operate in the same manner. Therefore,duplicate description of the rectifier 221, the capacitor 222, theinverter 223, and the impedance matching circuit 230 will be omittedherein.

Referring to FIGS. 2 and 10, the transformer 226 may be inductivelycoupled to a wiring between the impedance matching circuit 230 and theinverter 223. The transformer 226 may generate a signal (for example, asecond signal) similar to a signal (for example, a first signal)provided to the impedance matching circuit 230 and may output thegenerated signal to the filter 227. A voltage of the first signal may bean output voltage VO, and a current of the first signal may be an outputcurrent IO.

A voltage of the second signal may have a level determined by theinductive coupling from the output voltage VO. A current of the secondsignal may have an amount determined by the inductive coupling from theoutput current M. A phase of the current of the second signal may be thesame as a phase of the output current IO or may have a predeterminedphase difference (for example, 180 degrees).

The filter 227 may perform high-pass filtering or low-band rejectionfiltering on the second signal output from the transformer 226. Forexample, the filter 227 may remove a DC component of the second signal.The filter 227 may output a filtered current IF to the comparator 228.

The comparator 228 may detect phase information CI from the filteredcurrent IF. The phase information CI may include information on thephase of the output current M. The phase information CI is transmittedto the controller 225. The controller 225 may detect a phase difference(or delay time) between the output voltage VO and the output current IOusing at least one of switching signals SW and the phase information CI.

The controller 225 may adjust a frequency fsw of the output voltage VObased on the detected phase difference (or the delay time). When thefrequency fsw of the output voltage VO is adjusted, the phase differencebetween the output voltage VO and the output current JO is adjusted asdescribed with reference to FIGS. 5 to 9. The controller 225 may adjustthe frequency fsw of the output voltage VO such that the phases of theoutput voltage VO and the output current IO are rendered to be equal (orno delay time exists) or the phase difference (or delay time) fallswithin a predetermined range VO.

FIG. 11 is a block diagram illustrating an example of the controller 225in FIG. 10. Referring to FIGS. 2, 10, and 11, the controller 225includes a pulse width modulation (PWM) generator 225 a, a phasedetector 225 b, and a frequency adjuster 225 c. The PWM generator 225 amay control first to fourth switching signals SW1 to SW4. For example,the PWM generator 225 a may control frequencies, dead times,freewheeling intervals, and the like of the first to fourth switchingsignals SW1 to SW4.

The phase detector 225 b may receive the first switching signal SW1 andreceive phase information CI. The phase detector 225 b may distinguishdelay time PI or a phase difference from the first switching signal SW1and the phase information CI. The delay time PI is transmitted to thefrequency adjuster 225 c. The frequency adjuster 225 c may control thePWM generator 225 a through a control signal CTRL.

For example, the frequency adjuster 225 c may control the control signalCTRL such that the frequencies of the first to fourth switching signalsSW1 to SW4 are increased, decreased, or maintained by a predeterminedunit in response to the delay time PI. The frequency adjuster 225 c maycontrol the control signal CTRL such that the frequencies of theswitching signals SW1 to SW4 are increased, decreased, or maintained bya value corresponding to the delay time PI with reference to apredetermined lookup table.

For example, the frequency adjuster 225 c may include a calculator (notshown) configured to calculate a frequency adjustment amountcorresponding to the delay time PI using a predetermined function. Thefrequency adjuster 225 c may control the control signal CTRL such thatthe frequencies of the first to fourth switching signals SW1 to SW4 areincreased, decreased, or maintained according to an operation result ofan operator.

FIG. 12 illustrates an example in which a filtered current IF and phaseinformation CI are detected from an output current IO. In FIG. 12, thehorizontal axes indicate time T, and vertical axes indicate an outputcurrent IO, a filtered current IF, and phase information CI,respectively. Referring to FIGS. 2, 10, 11, and 12, the filtered currentIF may have the same phase as the output current IO. No delay time mayexist between the filtered current IF and the output current IO.

The phase information CI is a result of comparing the filtered currentIF with the comparator 228. When the filtered current IF has a positivevalue, the phase information CI has a high level. When the filteredcurrent IF has a negative value, the phase information CI has a lowlevel. Accordingly, the phase information CI may be the result ofdetecting only phase information in the filtered current IF.

FIG. 13 illustrates an example of phases of a first switching signal SW1and an output voltage VO. Referring to FIGS. 2, 10, 11, and 13, when thefirst switching signal SW1 has a high level, the output voltage VO has ahigh level. When the second switching signal SW2 has a high level (forexample, a ground level), the output voltage VO has a low level (forexample, a negative voltage).

That is, a phase of the first switching signal SW1 matches a phase ofthe output voltage VO. Accordingly, the phase of the first switchingsignal SW1 may be used as the phase of the output voltage VO withoutdetecting the phase of the output voltage VO. As an example, the thirdswitching signal SW3 may be used in the same manner as the firstswitching signal SW1. Accordingly, the third switching signal SW3 may beused instead of the first switching signal SW1.

FIG. 14 illustrates an example of a method of controlling a frequency ofan output voltage by a power supply. Referring to FIGS. 2, 10, 11, and14, the controller 225 may detect delay time PI of the output current IOwith respect to the output voltage VO in operation S110. For example,the phase detector 225 b may compare the first switching signal SW1 withthe phase information CI to detect delay time PI.

In operation S120, the controller 225 determines whether the delay timePI is less than the first time T1. For example, the first time T1 may be−5 ns. When the delay time PI is less than the first time T1, the outputcurrent IO has a negative delay with respect to the output voltage VO.That is, the phase of the output current IO leads the phase of theoutput voltage VO.

In operation S130, the frequency adjuster 225 c may increase thefrequencies of the first to fourth switching signals SW1 to SW4. As thefrequencies of the first to fourth switching signals SW1 to SW4 areincreased, the frequency of the output voltage VO is increased. When thefrequency of the output voltage VO is increased, the output current IOis delayed from the current phase, as described with reference to FIG.8. Accordingly, the delay time PI is increased. Then, the controller 225performs operation S160.

When the delay time PI is not smaller than the first time T1, thecontroller 225 determines whether the delay time PI is greater thansecond time T2 in operation S140. For example, the second time T2 may be15 ns. When the delay time PI is greater than the second time T2, theoutput current IO has a positive delay with respect to the outputvoltage VO. That is, the phase of the output current IO lags behind thephase of the output voltage VO.

In operation S150, the frequency adjuster 225 c may decrease frequenciesof the first to fourth switching signals SW1 through SW4. As thefrequencies of the first to fourth switching signals SW1 to SW4 aredecreased, the frequency of the output voltage VO is decreased. When thefrequency of the output voltage VO is decreased, the output current JOleads the current phase as described with reference to FIG. 6.Accordingly, the delay time PI is decreased. Then, the controller 225performs operation S160.

In operation S160, the controller 225 determines whether the delay timePI is greater than or equal to the first time T1 and less than or equalto the second time T2. For example, the controller 225 may determinewhether the delay time PI falls within the range defined by the firstand second times T1 and T2. When the delay time PI falls within thepredetermined range, the controller 225 may terminate the frequencyadjustment (or phase adjustment). When the delay time PI does not fallwithin the predetermined range, the controller 225 may perform operationS110 again.

As an example, in a power supply system in which a resonant frequency ofthe load 240 varies depending on environmental change, the controller225 may return to operation S110 to continue to perform frequencymonitoring.

FIG. 15 illustrates another example of a method of controlling afrequency of an output voltage VO by a power supply 220. Referring toFIGS. 2, 10, 11, and 15, in operation S210, the controller 225 maycalculate an average of delay time PI of the output current JO to theoutput voltage VO.

For example, the phase detector 225 b may store k delay times that arecontinuously detected (k being a positive integer). When the k delaytimes are stored, the phase detector 225 b may calculate an average ofthe delay times. As an example, the controller 225 may adjust a value ofk when an environmental change is detected, the value of k may beadjusted according to a request of the external device or a user'srequest. As another example, the value of k may be a fixed value that isnot be changed.

When the average of the delay times is calculated, the phase detector225 b may output an average of the delay times as delay time PI. Afteroutputting the delay time PI, the phase detector 225 b may reset (forexample, erase) the stored delay times. The phase detector 225 b maystart to collect the k delay times to calculate the next average.

In operation S220, the controller 225 determines whether the delay timePI is less than the first time T1. When the delay time PI is less thanfirst time T1, the frequency adjuster 225 c may increase frequencies ofthe first to fourth switching signals SW1 to SW4 in operation S230. Asthe frequencies of the first to fourth switching signals SW1 to SW4 areincreased, the frequency of the output voltage VO is increased.

When the delay time PI is not less than the first time T1, thecontroller 225 determines whether the delay time PI is greater than thesecond time T2 in operation S240. When the delay time PI is greater thanthe second time T2, the frequency adjuster 225 c may decrease thefrequencies of the first to fourth switching signals SW1 to SW4 inoperation S250. As the frequencies of the first to fourth switchingsignals SW1 to SW4 are decreased, the frequency of the output voltage VOis decreased.

In operation S260, the controller 225 determines whether the delay timePI is greater than or equal to the first time T1 and less than or equalto the second time T2. For example, the controller 225 may determinewhether the delay time PI falls within the range defined by the firstand second times T1 and T2. When the delay time PI falls within apredetermined range, the controller 225 may terminate the frequencyadjustment (or phase adjustment). When the delay time PI does not fallwithin the predetermined range, the controller 225 may perform theoperation S210 again.

FIG. 16 illustrates another example of a method of controlling afrequency of an output voltage VO by a power supply 220. Referring toFIGS. 2, 10, 11, and 16, in operation S310, the controller 225 maydetect the delay time PI of the output current IO to the output voltageVO. In operation S320, the controller 225 determines whether the delaytime PI is less than the first time T1. When the delay time PI is lessthan the first time T1, the phase detector 225 b may increase the firstcount in operation S330. Then, the controller 225 may perform operationS370.

When the delay time PI is not less than the first time T1, thecontroller 225 determines whether the delay time PI is greater than thesecond time T2 in operation S340. When the delay time PI is greater thanthe second time T2, the phase detector 225 b may increase the secondcount in operation S350. Then, the controller 225 may perform operationS370. When the delay time PI is not greater than the second time T2, thephase detector 225 b may increase the third count in operation S360.Then, the controller 225 may perform operation S370.

In operation S370, the controller 225 determines whether a maximum loopwas performed. For example, a single loop may include operations S310 toS360. The controller 225 may determine that the maximum loop wasperformed when the number of times the loops were performed reaches k (kbeing a positive integer). As an example, the controller 225 may adjustthe value of k when an environmental change is detected, according to arequest of an external device or a user's request. As another example,the value of k may be a fixed value that is not changed.

When the maximum loop was not performed, the controller 225 may startthe next loop in operation S310. When the maximum loop was performed,the controller 225 may reset the number of times the loops wereperformed and perform operation S390. In operation S390, the controller225 may determine whether the third count is dominant. For example, whenthe third count is greater than or equal to k/3, then the third countmay be dominant.

When the third count is dominant, the controller 225 may terminateadjustment of the delay time. When the third count is not dominant, thecontroller 225 may perform operation S390. In operation S390, thecontroller 225 may increase the frequencies of the first to fourthswitching signals when the first count is dominant. The controller 225may decrease the frequencies of the first to fourth switching signalswhen the second count is dominant.

As discussed above, the controller 225 may adjust a frequency fsw of theoutput voltage VO by collecting the k delay times and voting dominantone of the delay times. As an example, when n delay times (n being apositive integer less than k) less than the first time T1 aresuccessively detected, the controller 225 increases the frequencies ofthe first to fourth switching signals without voting. Then, the numberof times the loops were performed and the collected delay times may beinitialized and operation S310 may be performed.

As an example, when n delay times greater than the second time T2 aresuccessively detected, the controller 225 may decrease the frequenciesof the first to fourth switching signals without voting. Additionally,when n delay times smaller than the first time T1 are successivelydetected, the controller 225 may increase the frequencies of the firstto fourth switching signals without voting. Then, the number of timesthe loops were performed and the collected delay times may beinitialized and operation S310 may be performed.

FIG. 17 illustrates another example of a method of adjusting a frequencyof an output voltage VO by a power supply 220. Referring to FIGS. 2, 10,11, and 17, in operation S410, the controller 225 may detect the delaytime PI of the output current IO to the output voltage VO. In operationS415, the controller 225 determines whether the delay time PI is lessthan the first time T1. When the delay time PI is less than the firsttime T1, the phase detector 225 b may increase the first count and resetthe second and third counts in operation S400.

Then, in operation S425, the controller 225 may determine whether thefirst count reached a threshold value. When the first count is equal tothe threshold value, the controller 225 may increase a frequency inoperation S430. Then, operation S410 may be performed. When the firstcount is not equal to the threshold, operation S410 may be performedwithout adjusting the frequency.

When the delay time PI is not less than the first time T1, thecontroller 225 determines whether the delay time PI is greater than thesecond time T2 in operation S435. When the delay time PI is greater thanthe second time T2, the phase detector 225 b may increase a second countand reset the first and third counts in operation S440.

Then, in operation S445, the controller 225 may determine whether thesecond count reached a threshold value. When the second count is equalto the threshold value, the controller 225 may decrease the frequency inoperation S450. Then, operation S410 may be performed. When the secondcount is not equal to the threshold, operation S410 may be performedwithout adjusting the frequency.

When the delay time PI is not greater than the second time T2, the phasedetector 225 b may increase the third count and reset the first andsecond counts in operation S455. Then, in operation S460, the controller225 may determine whether the third count reached a threshold value.When the third count is equal to the threshold value, the controller 225may terminate the adjustment of the frequency. When the third count isnot equal to the threshold, operation S410 may be performed withoutadjusting the frequency.

As described above, when the delay times continuously exhibit the samecharacteristics, the controller 225 can adjust a frequency or terminatethe adjustment of the frequency according to the characteristics.

FIG. 18 illustrates an inverter 223′, an impedance matching circuit230′, and a load 240 according to an application example of the presentdisclosure. Referring to FIGS. 10 and 18, the inverter 223′ may includefirst to fourth transistors TR1 to TR4, first to fourth diodes D1 to D4,and an inductor Lzvs.

As compared to the inverter 123 in FIG. 2, the inverter 223′ furtherincludes an inductor Lzvs. The inductor Lzvs may be coupled betweenoutput nodes to which the output voltage VO is output. A current flowingthrough the inductor Lzvs may be an inductor current Izvs. The first tofourth transistors TR1 to TR4 and the first to fourth diodes D1 to D4may be connected and operate in the same manner as described withreference to FIG. 2.

FIG. 19 illustrates variations in an output current IO and an inductorcurrent Izvs with the lapse of time T. FIGS. 1, 19, and 19, a phase ofthe output voltage VO may match a phase of the output current IO. Theinductor current Izvs may act as a counter electromotive force of theoutput current IO. The inductor current Izvs has a negative value whenthe output current IO increases, and the inductor current Izvs may havea positive value when the output current IO decreases.

When the phases of the output voltage VO and the output current IO matcheach other, the output current IO may not flow during a dead time DT(see FIG. 4) in which the output voltage VO transitions from a highlevel to a low level. At this point, a positive current flows in theinverter 123′ due to the inductor current Izvs.

Similarly, when the phases of the output voltage VO and the outputcurrent IO match each other, the output current IO may not flow during adead time in which the output voltage VO transitions from a low level toa high level. At this point, a negative current flows in the inverter123′ due to the inductor current Izvs. Zero voltage nearly zero currentswitching (ZVZCS) may be achieved in the inverter 123′ due to theinductor current Izvs.

Power supplied to the load 240, for example, the amount of power perunit time may be controlled to precisely control the operation of theload 240. Various methods may be used to control the power supplied tothe load 240. FIG. 20 illustrates an example of a method of controllingpower depending on DC voltage conversion. Referring to FIG. 20, amaximum value of an output voltage VO may be adjusted depending on theDC voltage conversion.

When the DC voltage conversion is used, phases of the output voltage VOand an output current IO remain unchanged. Accordingly, the use of theDC voltage conversion results in an advantage that the operation of aninverter 220 is stable. On the other hand, the use of the DC voltageconversion needs a separate DC-DC converter configured to perform the DCvoltage conversion of a power supply VP. In addition, the use of the DCvoltage conversion encounters disadvantages that time is required toperform DC-DC conversion and a power control speed is low.

FIG. 21 illustrates an example of a method of controlling powerdepending on phase shift. Referring to FIG. 21, a phase differencebetween an output voltage VO and an output current IO may be adjusteddepending on phase shift. When an area of the overlapping region isreduced due to the phase difference between the output voltage VO andthe output current IO, power supplied to a load 240 is decreased.Accordingly, the power supplied to the load 240 a may be adjusted byadjusting a frequency fsw of the output voltage VO.

Since the power is adjusted by adjusting the frequency fsw of the outputvoltage VO, the power may be adjusted relatively rapidly. However, asdescribed with reference to FIGS. 5 to 9, stress may be applied to thefirst to fourth transistors TR1 to TR4 when the phases of the outputvoltage VO and the output current IO are different. Thus, stability ofthe inverter 220 (see FIG. 10) may be reduced.

FIG. 22 illustrates an example in which first to fourth switchingsignals SW1 to SW4 and an output voltage VO are adjusted according topulse width modulation. Referring to FIGS. 2 and 22, the first andsecond switching signals SW1 and SW2 may have the same phases as thosedescribed with reference to FIG. 3. The third and fourth switchingsignals SW3 and SW4 may have phases which lead those described withreference to FIG. 3.

The output voltage VO has a high level when both the first and thirdswitching signals SW1 and SW3 have a high level. When the phase of thethird switching signal SW3 leads the phase of the first switching signalSW1, a period in which both the first and third switching signals SW1and SW3 have a high level is reduced. Thus, a period in which the outputvoltage VO has a high level is reduced.

The output voltage VO has a low level when both the second and fourthswitching signals SW2 and SW4 have a high level. When the phase of thefourth switching signal SW4 leads than the phase of the second switchingsignal SW2, a period in which both the second and fourth switchingsignals SW2 and SW4 have a high level is reduced. Thus, the period inwhich the output voltage VO is low is reduced.

FIG. 23 illustrates an example of a method of controlling poweraccording to pulse width modulation. Referring to FIG. 23, a pulse widthof an output voltage VO may be adjusted using the pulse widthmodulation. When an area in which the output voltage Vo and an outputcurrent IO overlap each other is reduced, power supplied to the load 240(see FIG. 10) is decreased. Thus, the pulse width of the output voltageVO may be modulated to adjust the power supplied to the load 240.

However, when the pulse width of the output voltage VO is decreased,some of the first to fourth transistors TR1 to TR4 may be switched whenthe output current IO has a positive value or a negative value.Accordingly, stress may be applied to the first to fourth transistorsTR1 to TR4 and stability of the inverter 220 may be reduced.

FIG. 24 illustrates a method of supplying power according to an exampleembodiment of the present disclosure. Referring to FIGS. 2, 10, and 24,the controller 225 may adjust power supplied to a load (e.g., amount ofpower per unit time) through freewheeling insertion. As an example, sixperiods of the output voltage VO are shown in 24. To describe thepresent inventive concept, it will be assumed that six cycles are unittime. However, the unit time required to adjust the amount of power isnot limited to six periods of the output voltage VO.

In a high-power mode (HPM), the controller 225 may control the first tofourth switching signals SW1 to SW4 in the manner described withreference to FIG. 3 or FIG. 4. The output voltage VO may continuouslytransition, and the output current IO may also continuously transition.In a low-power mode (LPM), the controller 225 may control the first tofourth switching signals SW1 to SW4 according to a powering period and afreewheeling period.

A powering period may include first and second powering periods P1 andP2. In the first and second powering periods P1 and P2, the controller225 may control the first to fourth switching signals SW1 to SW4 in themanner described with reference to FIG. 3 or 4. A freewheeling periodmay include a first freewheeling period F1. In the first freewheelingperiod F1, the controller 225 may control the first to fourth switchingsignals SW1 to SW4 such that the output voltage VO does not have a highlevel and a low level (for example, has a ground level).

For example, in the first freewheeling period F1, the controller 225 maymaintain the first to fourth switching signals SW1 to SW4 at a lowlevel. Since the output voltage VO is not supplied, the current amountof the output current IO in the first freewheeling period F1 may besmaller than the current amount of the output current IO in the firstand second powering periods P1 and P2. The inverter 223 supplies powerto the load 240 in the first and second powering periods P1 and P2 anddoes not supply power to the load 240 in the first freewheeling periodF1.

The controller 225 may control the amount of power supplied to the load240 for a unit time by adjusting a total length of a powering period anda total length of a freewheeling period for the unit time. The longerthe freewheeling period, the less the amount of the power supplied tothe load 240. The shorter the freewheeling period, the more the amountof the power supplied to the load 240. As an example, the power amount Pmay be calculated by Equation (2).

$\begin{matrix}{P = {( {\frac{1}{\sqrt{2}} \times \frac{4}{\pi} \times {VVP} \times \frac{( {N - n} )}{N}} )^{2} \times \frac{1}{Rpla}}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

In Equation (2), VVP denotes a voltage at a power supply node VP, Ndenotes the number of total cycles included in a unit time, n denotesthe number of all freewheeling periods included in the unit time. As anexample, when the freewheeling period is adjusted in a half-cycle unit,N and n may be changed into the number of half-cycles. As shown inEquation (2), the power amount P may be adjusted according to a lengthof the powering period, that is, a length of the freewheeling period.

As an example, a freewheeling period may be distinguished from a deadtime DT (see FIG. 4) in that the freewheeling period has a lengthgreater than or equal to a half-cycle of the output voltage VO. The deadtime DT may be shorter than the half-cycle of the output voltage VO.When the dead time DT has a length corresponding to a half-period of theoutput voltage VO, the phases of the output voltage VO and the outputcurrent IO are changed in each cycle. Accordingly, the power supply 220does not operate normally.

FIG. 25 illustrates an example of a variation in an inductor currentIzvs when an output voltage VO has a freewheeling period. Referring toFIGS. 1, 25, and 27, a powering period of one cycle and a freewheelingperiod of one cycle may be alternately arranged. The inductor currentIzvs may be calculated using Equation (7).

$\begin{matrix}{I_{ZVS} = {{Iini} + {\frac{1}{L_{ZVS}}{\int_{0}^{\tau}{{{VO}(t)}dt}}}}} & {{Equation}\mspace{14mu} (3)}\end{matrix}$

In Equation (3), Iini denotes an initial current. During thefreewheeling interval, the inductor current Izvs remains negative. Sincethe sum total (or average current) of the inductor currents Izvs shouldbe zero, an absolute value of a positive peak value of the inductorcurrent Izvs may be greater than an absolute value of a negative peakvalue of the inductor current Izvs. When the amount of inductor currentIzvs flowing during the dead time DT varies, the inverter 123′ maynon-uniformly operate. Accordingly, the amount of current of theinductor current Izvs flowing during the dead time DT is preferablyuniform.

As an example, in FIG. 25, one freewheeling cell may include one periodin which the output voltage VO has a ground level. FIG. 25 shows threepowering cells and freewheeling cells. As another example, onefreewheeling cell may include one period in which the output voltage VOhas a high level and a low level, and one period in which the outputvoltage VO has a ground level. FIG. 25 may show three freewheelingcells.

FIG. 26 illustrates another example of a variation in an inductorcurrent Izvs when an output voltage VO has a freewheeling period.Referring to FIGS. 1, 18, and 26, a powering period of a half-cycle anda freewheeling period of a half-cycle may be alternately arranged. InFIG. 26, a positive peak value and a negative peak value of the inductorcurrent Izvs match each other.

However, when the output voltage VO has a negative value, the outputcurrent IO has a positive value. Power is supplied from the load 140 tothe inverter 123 when the output voltage VO and the output current IOhave phases opposite to each other, which may result in unnecessarypower consumption and may cause the load 140 to be turned off.Accordingly, the phases of the output voltage VO and the output currentIO preferably have the same sign.

As an example, in FIG. 26, a freewheeling cell may include a half-cyclein which the output voltage VO has a high level, a half-cycle in whichthe output voltage VO has a ground level, a half-cycle in which theoutput voltage VO has a low level, and a half-cycle in which in whichthe output voltage VO has a ground level. For example, FIG. 26 may showthree freewheeling cells.

FIG. 27 illustrates another example of a variation in an inductorcurrent Izvs when an output voltage VO has a freewheeling period.Referring to FIGS. 1, 18, and 27, a single freewheeling cell may havefour cycles. Two freewheeling cells are shown in FIG. 27.

A freewheeling cell includes one cycle in which the output voltage VOhas a high level and a low level, one cycle in which the output voltageVO is in a ground level, one cycle in which the output voltage VO is ina high level and a ground level, and one period in which the outputvoltage VO is in a ground level and a low level. A positive peak valueand a negative peak value of the inductor current Izvs match each other.Additionally, a sign of the output voltage VO and a sign of an outputcurrent IO match each other.

As illustrated in FIG. 27, a controller 125 may control a frequency fswof the output voltage VO such that the frequency fsw of the outputvoltage VO and a resonant frequency f0 of a load 140 match each other.Zero voltage nearly zero current switching (ZVZCS) may be achieved byinductors an inductor Lzvs. Also the controller 125 may controlfreewheeling cells such that a positive peak value and a positive peakvalue of the inductor current Izvs match each other. The controller 125may control freewheeling cells such that the sign of the output voltageVO and the sign of the output current IO match each other.

FIG. 28 is a block diagram of a power supply system including ahalf-bridge circuit according to another example embodiment of thepresent disclosure. Referring to FIGS. 1 and 28, an inverter 123′includes first and second transistors TR1 and TR2, first and seconddiodes D1 and D2, and first and second capacitors C1 and C2. Animpedance matching circuit 130 includes a capacitor C, and a load 140may be modeled as an inductor Lpla and a resistor Rpla.

As compared to the inverter 123 in FIG. 2, the inverter 123′ in FIG. 28includes the first capacitor C1 disposed instead of the third transistorTR3 and the third diode and the second capacitor C2 disposed instead ofthe fourth transistor TR4 and the fourth diode D4. Each of the first andsecond capacitors C1 and C2 has capacitance high enough to have aboth-end voltage which is substantially a direct current (DC). Theinverter 123′ in FIG. 28 may be a half-bride type inverter having halfan output voltage range and half a switch and half switching signals, ascompared to the inverter 123 in FIG. 2.

The inverter 223 of the power supply 220 described with reference toFIG. 10 may include the inverter 123′ shown in FIG. 18. As describedwith reference to FIG. 18, an inductor Lzvs may be applied to theinverter 123′, similarly to the inverter 223′. The present inventiveconcept to adjust a powering period and a freewheeling period describedwith reference to FIG. 24 may be identically applied to the inverter123′ in FIG. 24. In addition, the method of controlling (supplying)power described with reference to FIGS. 26 and 27 may be identicallyapplied to the inverter 123′ in FIG. 28.

According to the present disclosure, a pattern of switching signalsprovided to an inverter of a power supply is adjusted to adjust theamount of power or current supplied to a load. Accordingly, a powersupply and a method of supplying power, having improved performance andcausing noise and stress without increasing complexity, are provided. Inaddition, a frequency of an output voltage is adjusted depending on aphase difference between the output voltage and an output current, andthe phase difference is adjusted. Accordingly, a power supply and amethod of supplying power, automatically compensating for the phasedifference between the output voltage and the output current, areprovided.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the following claims.

What is claimed is:
 1. A power supply comprising: an inverter configuredto convert direct current (DC) power into alternating current (AC)power; an impedance matching circuit configured to supply the AC powerto a load; and a controller configured to detect a delay time of anoutput voltage and an output current output to the impedance matchingcircuit and the load and to adjust a frequency of the output voltageaccording to the detected delay time.
 2. The power supply as set forthin claim 1, wherein the controller increases the frequency of the outputvoltage when the detected delay time is less than a first time.
 3. Thepower supply as set forth in claim 2, wherein the controller decreasesthe frequency of the output voltage when the detected delay time isgreater than a second time.
 4. The power supply as set forth in claim 3,wherein the controller maintains the frequency of the output voltagewhen the detected delay time is less than or equal to the second timeand greater than or equal to the first time.
 5. The power supply as setforth in claim 1, wherein the controller calculates an average of delaytimes detected from the output voltage and the output current andincreases the frequency of the output voltage when the average is lessthan the first time.
 6. The power supply as set forth in claim 5,wherein the controller stores k detected delay times (k being a positiveinteger) and calculates an average of the k detected delay times.
 7. Thepower supply as set forth in claim 6, wherein the controller stores thesubsequent k detected delay times and calculates the average of the kdetected delay times after calculating the average and adjusting thefrequency of the output voltage depending on the calculated average. 8.The power supply as set forth in claim 6, wherein the controller adjuststhe k.
 9. The power supply as set forth in claim 1, wherein thecontroller increases the frequency of the output voltage when, amongdelay times detected from the output voltage and the output current,delay times less than a first time are dominant.
 10. The power supply asset forth in claim 9, wherein the controller determines that the delaytimes less than the first time are dominant, when the number of thedelay times less than the first time is greater than or equal toone-third of the number of the detected delay times.
 11. The powersupply as set forth in claim 9, wherein the controller stores k detecteddelay times (k being a positive integer) and determines dominant delaytimes among the stored k detected times.
 12. The power supply as setforth in claim 11, wherein the controller immediately increases thefrequency of the output voltage without determination of the dominantdelay times when n continuous delay times (n being a positive integerless than k) are less than the first time.
 13. The power supply as setforth in claim 1, further comprising: a transformer inductively coupledto a wiring between the inverter and the load and configured to output afirst signal having a current of the same phase as an output currentprovided to the load; and a comparator configured to output a secondsignal indicating the phase of the output current from an output signalof the transformer and to output the second signal to the controller.14. The power supply as set forth in claim 13, wherein the invertercomprises: a first transistor and a first diode coupled in parallelbetween a power supply node and a first output node; a second transistorand a second diode coupled in parallel between the first output node anda ground node; a third transistor and a third diode coupled in parallelbetween the ground node and a second output node; and a fourthtransistor and a fourth diode coupled in parallel between the powersupply node and the second output node, the first output node and thesecond output node are connected to the impedance matching circuit, andthe controller controls respective voltages of gates of the first tofourth transistors.
 15. The power supply as set forth in claim 14,wherein the controller adjusts the frequency of the output voltagedepending on a phase difference between the second signal and aswitching signal provided to the first transistor.
 16. The power supplyas set forth in claim 14, wherein the inverter further comprises: aninductor coupled between the first output node and the second outputnode.
 17. The power supply as set forth in claim 1, wherein thecontroller is further configured to adjust dispositions of a poweringperiod, in which the inverter outputs the AC power, and a freewheelingperiod, in which the inverter does not output the AC power, such thatthe inverter adjusts an amount of power per unit time supplied to theload through the impedance matching circuit.
 18. The power supply as setforth in claim 1, wherein the controller adjusts the frequency of theoutput voltage according to the same characteristics when the delaytimes continuously exhibit the same characteristics.
 19. A method ofsupplying power to a load, the method comprising: detecting a delay timeof an output voltage and an output current output to the load; andadjusting a frequency of the output voltage depending on the detecteddelay time.
 20. The method as set forth in claim 19, wherein thedetecting and the adjusting are repeated until the delay time fallswithin a predetermined range.
 21. The method as set forth in claim 19,wherein the delay time includes an average of delay times.
 22. Themethod as set forth in claim 19, wherein the adjusting comprises:storing delay times; counting the number of delay times less than afirst time, among the stored delay times, as a first count; counting thenumber of delay times greater than a second time, among the stored delaytimes, as a second count; counting the number of delay times greaterthan or equal to the first time and less than or equal to the secondtime as a third count; and adjusting the frequency of the output voltagedepending a dominant count among the first to third counts.
 23. Themethod as set forth in claim 19, wherein the adjusting comprises:adjusting the frequency of the output voltage according to the samecharacteristics when delay times continuously exhibit the samecharacteristics.
 24. The method as set forth in claim 19, furthercomprising: receiving a target power amount; comparing an amount ofpower supplied to the load with the target power amount; adjusting apowering period, in which alternating current (AC) power is supplied tothe load, and a freewheeling period, in which the AC power is notsupplied to the load, such that the target power amount and the amountof power per unit time become equal to each other, depending on acomparing result; and supplying power to the load according to theadjusted powering and freewheeling periods.